(a) Technical Field
The present disclosure relates generally to automotive technologies, and more particularly, to a manual park release device for a transmission of a vehicle.
(b) Background Art
In traditional transmission shifting systems, transmission modes (e.g., park, neutral, reverse, drive, etc.) can be changed using mechanical links between the gear shifter and the transmission. However, in vehicles using a shift-by-wire (SBW) system, the transition between transmission modes is accomplished through electronic controls without any mechanical links between the gear shifter and the transmission. SBW systems can save space in the vehicle by eliminating space required for housing the mechanical links found in traditional shifting systems. Further, due to the elimination of mechanical links between the gear shifter and transmission, minimal effort is required on behalf of the driver during gear selection, as many SBW systems allow for shifting through the press of a button or a switch. SBW systems also provide for improved calibration and smoothness of shifts in particular circumstances, as compared to traditional shifting systems.
Problematically, in the event of a power failure, a SBW system may be unable to shift out of the park range, as the driveline of the vehicle is locked. It is therefore very difficult for such vehicle to be towed when the driveline is locked. To address this problem, a manual park release device can be used to override the SBW system and manually remove the transmission from the park range (into neutral, for example). Conventional manual park release devices generally include a manually operated lever which, when operated, actuates a cable that is connected to the transmission in such a manner as to pull the transmission from the park range, or at least unlock the driveline.
When the transmission has been brought out of the park range, it is beneficial for the manual park release device to include functionality for keeping the transmission in the out-of-park range, as well as allowing the transmission to return to the park range (e.g., after the vehicle has been towed). To this end, some conventional manual park releases comprise a locking mechanism and a spring-bias that tends to return the transmission to the park range. When the operator pulls the manual park release device (against the spring-bias) into a position corresponding to a disengaged P-range, the locking mechanism can lock the manual park release device in place. Then, to return the transmission to the park range, the operator can unlock the locking mechanism, so the manual park release device can return to the position corresponding to the park range, thereby allowing the transmission to return to the park range.
However, such manual park release devices typically require two hands for operation, namely, one hand for operating the manual park release lever and the other for operating the locking mechanism. This can be particularly cumbersome when the manual park release device is positioned in a position that is difficult to access, such as underneath the center console or near the trunk of the vehicle, and the driver is required to keep his or her foot on the brake (i.e., so the vehicle does not roll when it is pulled out of park into neutral). Moreover, a tool is often required for disengaging a plunger or the like prior to pulling the manual park release lever.